The present invention relates to a non-iron core, brushless, axial magnetic field permanent-magnet type DC motor, and more particularly to such a DC motor suitable for medium and low speed, high torsion and high power output operation.
A regular non-iron core, brushless, permanent-magnet type DC motors commonly have windings (coils or printed circuits) at one side, forming axial magnetic fields at one side. When a DC motor of this type is used, it is controlled by a two phase four wire type four state electronic phase control system, i.e., electric current is caused to reverse its direction at the phase difference of 180.degree.. Because the windings induce magnetic fields only at one side, the rotor or stator receives force only from one side, causing the rotation unstable. Because electric current is caused to reverse its direction at the phase difference of 180.degree., the magnetic repulsion from the single-sided windings acting at one side of the permanent steel magnets utilizes only 50% of the electromaginctic fields, and the output of torsion is limited. Further, this 180.degree. phase difference may cause the motor unable to function well at a particular angle, or cause the motor to vibrate during a low speed operation.